Lake Karachay, Russia
If the above mentioned lakes are dangerous because of their natural environment and all those dangers are not caused by people, then Lake Karachay is an absolutely different story. This lake is situated in Russia and is known as the deadliest spot on our planet. The level of radiation is outrageous and staying around the lake for longer than half an hour can kill you. Forty years ago the lake served as a dumping ground. It was used to bury nuclear waste. Later on people realized the tragedy and since 1990 there have been attempts to save the place. People placed concrete blocks in the lake hoping that the blocks will absorb the radiation. How successful their plan is would be hard to predict at present.